Sunday, 22 September 2013

Researchers have long struggled to design surveys that collect detailed and informative data without introducing bias through the use of loaded, confusing, or restrictive wording. A team of French researchers has come up with a novel solution to this problem: Toss out the surveys altogether, and replace them with a virtual computer program that allows respondents to express their thoughts and preferences in actions rather than in words.

This is the idea behind Virtual Garden, a program that allows users to select from 95 different features in order to create their ideal garden. The features fall within seven different categories: animals, flowers, lawn and cover, sport and playing, trees and bushes, water, and other. The program keeps track of each item that is added and adjusted, and calculates biodiversity as biotic features are introduced into the virtual habitat. Users are able to view the garden from multiple angles and even take a virtual stroll through the area in order to evaluate their progress and determine whether further manipulations need to be made to the environment.

Far from being merely a nerdy new version of The Sims, the program was designed to assess which features people most want to experience when they visit public gardens. Further, an analysis of the virtual habitats could help clarify the role that biodiversity has in driving humans' overwhelmingly positive responses to green spaces--particularly those located in otherwise urban areas. Finally, by collecting basic social, economic, and demographic information about each program user, the program's developers can also assess whether habitat preferences are influenced by age, education, income, and general interest in the natural environment.

The research team responsible for Virtual Garden trialled the program among 732 Parisian hospital patients. Each individual was given a 30-minute time limit for designing the garden, though the average length of time required was only 19.2 minutes. Gardens typically contained approximately 24 different features--9 "objects" (such as ponds), 5 animals, 8 flowers, and 5 woody species (trees or bushes). Overall, users included fewer biotic features than were expected by chance. Animals were particularly underrepresented, with nearly a third of gardens containing no animals at all, and almost another third containing fewer than 5 animal species. Larger animals--especially mammals and herptiles--were not very popular; the least preferred species overall were foxes and chimpanzees. Ladybugs, peacocks, and great tits, on the other hand, were the most preferred. The most popular species were generally those that are common in Parisian gardens, suggesting that patients tended to populate their virtual gardens with species that are most familiar to them.

Several demographic and socioeconomic factors influenced garden design. For example, men included fewer animals and flowers than women; younger patients included more non-native species; and people who showed a greater interest in conservation and nature activities tended to create gardens with higher biodiveristy. Interestingly, plant richness was higher in gardens created by people who grew up in more rural areas, again suggesting that familiarity with species is an important driver of habitat preferences.

The Virtual Garden trial produced two main results. First, it suggests that computer programs may be a useful way to collect data from people without accidentally introducing bias into a study. Such programs are likely to be particularly useful in situations where researchers need to address or describe situations that are highly visual in nature--such as habitat structure, the aesthetics of which can greatly influence respondents' attitudes and opinions. Second, the patterns reported here get us one step closer to understanding city-dwellers' complex and often contradictory responses to green spaces. There is particularly strong evidence of an "extinction-of-experience" process, whereby people judge biodiversity and aesthetics according to what they have previously experienced, rather than what may be natural, healthy, and/or desirable in a given environment.

The creators of the Virtual Garden hope that conservationists and managers can use their program to collect and compare data from across a wide geographic range, and, therefore, to improve our "understanding of the role culture and living context...play in people's relations with biodiversity." This could not only help save threatened species, but also improve the well-being of people by increasing and improving human-nature interactions even in the most urban of environments.

Saturday, 21 September 2013

Szechuan peppers, which are responsible for spicing up a variety of Asian dishes, are considered unique among peppers for their "lemony overtones" and the tingling, almost electric, sensation that they cause in the mouths of consumers. The latter has been attributed to a compound known as hydroxyl alpha sanshool (also known simply as sanshool), but the neurological mechanism responsible for the effects of sanshool has not previously been understood. This inspired a research team from the University College London to perform a suite of experiments characterizing how eaters perceive Szechuan peppers, and exploring the sensory processes influencing these experiences. Their results suggest that the ubiquitously identified tingling sensation is produced by the activity of "rapidly adapting" (RA) sensory nerves that are more generally associated with mechanical, rather than chemical, stimuli.

(Szechuan pepper, also known as Sichuan or Szechwan pepper. There are at least two species responsible for this spice. Although the husk is generally considered the most important part of the plant for culinary purposes, some cooks may also work with leaves. The peppers may also be used in medicine. Image courtesy of Wikimedia.)

In the first portion of their study, the researchers applied a pepper solution to the lower lips of 12 volunteers; additional volunteers were also treated with ethanol and water control solutions. Each volunteer was asked to indicate whether his/her treatment produced a tingling, burning, cooling, warming, and/or numbing sensation. All individuals treated with the pepper solution agreed that it felt tingly. Although some people also described the ethanol treatment in this way, they indicated that the pepper solution resulted in a unique sensation that was both more intense and associated with a regular pulse.

The nature of this temporal effect was explored in more detail in the second part of the study. Volunteers were again treated with a swab of pepper solution applied to their lower lips. Once the tingling sensation began, the researchers applied a mechanical vibration to each volunteer's index finger, then asked the volunteers to indicate whether this vibration was of a higher or lower frequency than the feeling in their lips. Participant responses were used to adjust the frequency after each trial, thus allowing the researchers to gradually narrow in on the exact frequency of the pepper stimulus. Volunteers converged on a mechanical vibration frequency of 50.0 Hz, which happens to be near the midpoint of the range of frequencies (10-80 Hz) to which RA1 afferent fibers are most sensitive.

(Afferent nerves such as the RA1 are responsible for relaying information from sense organs, including skin, back to the brain. Image courtesy of Wikipedia.)

To double-check the legitimacy of comparing vibrations between lips and fingers, the researchers performed a third experiment in which eight volunteers were asked to compare the vibration frequencies of stimuli applied to first their lips and then their fingers, with a 1.5-s delay in between. Volunteers were most sensitive to convergence at a slightly lower frequency than that identified in the second experiment (46.4 Hz vs. 50.0 Hz). However, these two values are quite close, and the results clearly show that people are capable of relating sensations between fingers and mouths--suggesting that the researchers had come up with a suitable method for estimating pepper vibration frequencies.

In the final portion of the study, volunteers were exposed to both the mechanical and pepper stimuli sequentially. Because nerves need to "reset" between stimulus events, the second stimulus should have a lesser effect than the first--but only if both stimuli are activating the same set of nerves. After being exposed to an initial "adaptation stimulus" to their lips, volunteers were treated again with either a mechanical vibration or a pepper swab. A mechanical vibration was then applied to their fingers, and volunteers were asked to report on whether the frequency of this stimulus was higher or lower than that on their lips. As expected, volunteers had difficulty pinpointing the frequency of the second treatment, indicating that their nerves were still recovering from the adaptation stimulus. This was true regardless of whether the second treatment was a mechanical vibration or a pepper swab. In other words, both types of stimuli probably activate the same nerves.

(Hydroxy alpha sanshool, the compound responsible for the tingling sensation caused by Szechuan pepper. Gourmands might consider adding this chemical to their dishes in order to change the perception of other flavors, or to help diners experience food both chemically and mechanically. Image courtesy of Wikimedia.)

Taken together, results from the four experiments strongly suggest that the "light-touch" RA1 nerves are responsible for creating the tingling sensation that results from eating Szechuan pepper. Although sanshool is known to activate at least four other types of nerve fibers, a variety of factors--including the locations of those fibers and the types of sensation that sanshool produces when interacting with them--suggest that RA1 nerves are the most important player in producing a response to pepper-laden foods.

The authors suggest that these results may help us better understand the "pins and needles" sensations that are associated with some injuries and neural abnormalities. On a more fun note, however, they also point out that their findings may be of interest to gastronomists interested in enhancing their eating experiences. Szechuan pepper may not be the only food that influences taste by mimicking touch; we should be on the lookout for others that might similarly spice up our meals, both literally and figuratively. Further, because of the simultaneous chemical and mechanical effects of Szechuan peppers, chefs may be able to alter other flavors--or diners' perceptions of them--by adding sanshool to their culinary creations.

Who is the "Anthrophysist"?

I am a biologist who studies the ways in which anthropogenic disturbance impacts animals (especially birds). I hope that the results of my work, and the work of other researchers like me, can help humans learn how to coexist more peacefully with wildlife. I am also interested in the role that nature has played in shaping human cultures around the world and over the centuries. Although this blog will predominantly focus on scientific research, I hope to occasionally profile some anthropological work as well, in order to better highlight the interconnectedness of humans ("anthro") and nature ("physis").